Firestik 2 threaded ajuster too short

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original45
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Firestik 2 threaded ajuster too short

Post by original45 » 04 Dec 2018, 20:37

Got a 5' firestik 2 with the threaded swr adjustment at top. It's slightly too short as it spears swr would drop further if I didn't run out of threads on standard rod.

Seems a strange course thread anyone found suitable rod to replace or had this problem. I'm guessing 1/2" extra would suffice.

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ch25
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Re: Firestik 2 threaded ajuster too short

Post by ch25 » 04 Dec 2018, 21:04

Maybe it is mounting location influence.
You can't have too many antennas...

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Re: Firestik 2 threaded ajuster too short

Post by original45 » 04 Dec 2018, 22:25

I will try it again Chris, but it is the second attempt with it as I now have a suitable 3/8 magmount ,the last test was on a friend's mag but I'm getting same on mine.
Don't get me wrong it's ok but I know if it were longer I'd get even lower.

Will try again in the week.
Cheers again chris

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Re: Firestik 2 threaded ajuster too short

Post by Tim » 04 Dec 2018, 23:18

Sounds like by what you say that some previous has cut the threaded end to SWR instead of the other end of it. Find a length of steel or brass wire the same dia and thread it to the length you require with an appropriate thread die.

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Re: Firestik 2 threaded ajuster too short

Post by Tim » 04 Dec 2018, 23:19

Sounds like by what you say that some previous has cut the threaded end to SWR instead of the other end of it. Find a length of steel or brass wire the same dia and thread it to the length you require with an appropriate thread die.

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Clipper
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Re: Firestik 2 threaded ajuster too short

Post by Clipper » 05 Dec 2018, 08:19

You can get 3/8" x 24tpi couplers on ebay which can add the length at the bottom on the antenna. Example (BPN30) here

The nut that comes with a lot of 3/8 threaded antennas is meant for adjusting length at the bottom too.

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Re: Firestik 2 threaded ajuster too short

Post by Tim » 05 Dec 2018, 09:14

The threaded stud length at the base makes no difference to the SWR adjustment as it's below the coil and has no influence on the electrical length of most mobile antennas.

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Re: Firestik 2 threaded ajuster too short

Post by Clipper » 05 Dec 2018, 10:16

It's all one radiator - why do centre/top loaded antennas work?

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The Collector
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Re: Firestik 2 threaded ajuster too short

Post by The Collector » 05 Dec 2018, 12:51

Tim wrote:
05 Dec 2018, 09:14
The threaded stud length at the base makes no difference to the SWR adjustment as it's below the coil and has no influence on the electrical length of most mobile antennas.
So one of these wouldn't make any difference then?

https://rover.ebay.com/rover/0/0/0?mpre ... 0830120834

It's the only reason I can think of why someone would buy one :)

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Re: Firestik 2 threaded ajuster too short

Post by Tim » 05 Dec 2018, 14:22

That GP unit would do absolutely nothing for the radiation pattern, your vehicle is the ground plane, if anything it would probably upset it.

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Re: Firestik 2 threaded ajuster too short

Post by The Collector » 05 Dec 2018, 14:58

As it screws onto the aerial itself rather than the magnetic base/ground-plane, surely it shouldn't noticably affect the radiation pattern?
I was thinking if it physically added an inch onto the height of the aerial, it might mean the top-screw could then be adjusted more.

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Re: Firestik 2 threaded ajuster too short

Post by original45 » 06 Dec 2018, 14:25

Anyone know what thread size type it is on the ajuster rod please

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